1. Field of the Invention
This invention relates to a medication injection device which, upon being activated by the user, delivers medication from a syringe with needle to the user with the needle being in a retracted, hidden position at all times except when actual injection occurs. More particularly, this device permits treatment of appropriate cases of male erectile dysfunction by accurate placement and introduction of substances into the erectile bodies (corpora cavernosa) of the penis.
2. Description of the Related Art
It is well known that many persons are apprehensive of receiving an injection from a hypodermic needle. This situation is worsened for those who must administer their own injections, such as diabetic patients and others who regularly require medication or who require that medication be administered in private or in emergency situations, such as acute allergies to insect bites (anaphylaxis), hypoglycemic reactions, etc. This apprehension is particularly acute in the treatment of male erectile dysfunction with direct injection of medication into the penis.
While the invention is intended to be used in conjunction with the administration of medicine of any physical form to various parts of the body and to various tissue depths, it is particularly applicable for use in the treatment of erectile dysfunction.
Defined simply, erectile dysfunction occurs when a male is unable to maintain adequate penile rigidity necessary to initiate, sustain and successfully consummate the act of coitus. It denotes organic impotence.
This condition can be a psychologically devastating therapeutic problem. It has been estimated to effect 50% of all diabetic men and up to 9% of younger men in apparent good health. Varying degrees of erectile dysfunction caused by age, drug use, arteriosclerosis, trauma, hormone disorders and surgical procedures have also been observed. Diminished male erectile response is the limiting factor in sexual relationships. The fear of erectile failure has been reported as one of the primary reasons for decreased libido in older males.
The penile erection mechanism of the normal male is a complex interaction of hormones, neurotransmitters and blood vessels. An erection begins when paired penile arteries dilate in response to neurotransmitters relaxing the smooth muscle walls of the arteries. An increased incoming blood flow engorges the chambers of the penis (corpora cavernosa) where it is trapped. The tough and fibrous encasing tunica albuginea is stretched by tumescence and compresses perforating veins which drain the blood filled chambers. Venous drainage is impeded and further penile rigidity ensues. In organic impotent males, this vascular-erection mechanism is substantially impaired, not activated or not intact.
Self-injection of vasoactive pharmacotherapeutic agents directly into the penis for treatment of erectile dysfunction is known. Intracavernous papaverine, phentolamine and prostaglandin E.sub.1 frequently are used individually or in synergistic mixtures to replace the absent neurotransmitter mediated vascular dilatation and subsequent physiologic erection. Nitric oxide or a natural neuro-transmitter-hormone, vasoactive intestinal peptide, may be the future vasoactive agents of choice.
While clinical success with intra-cavernous pharmacotherapy exceeds 75%, many patients do not initiate or abandon self-injection therapy once it has been tried. The most common reason self-injection is not used is a universal phobia of introducing a needle into one's penis. Other reasons include on older patient's ineptitude, manual tremors and loss of dexterity necessary to locate injection site; physical handicaps of blindness, loss of limb and abdominal obesity; transportation inconvenience; prolonged syringe needle-vial drawing techniques; lack of spontaneity during love making; objections from sexual partner; and lack of self-injection confidence, plus the natural apprehensions that professional assistance is required to avoid hemorrhage or priapism.
Various types of syringes have been developed for injecting drugs into the penis or for self-administration of drugs into other parts of the body. These devices, which have proved ineffective for various reasons, include the one shown in U.S. Pat. No. 4,150,669 to Latorre. A dual hypodermic needle syringe for injecting fluids into the penis is shown, which has two parallel, interconnected barrels connected to needles extending from the barrels. This device has the disadvantage that the syringe needles must be manually introduced into the penis and manual depression of the plunger(s) is required to inject the medicinal fluid from the syringe and needle into the penis.
Various forms of spring-equipped syringe holders and actuators are known, such as the ones shown in U.S. Pat. Nos. 3,941,130 (Tibbs), 4,261,358 (Vargas et al.) and 4,188,950 (Wardlaw). However, these devices do not utilize a mechanism which allows for automatic insertion of the needle, injection of the fluid, and retraction of the needle provided in a compact, discrete device.
Thus, there exists the need for an automatic injection device which allows easy and accurate self-injection of medication. This need is particularly acute in the self-injection of medication into one's penis where there is the additional need of keeping the needle hidden from view to eliminate needless anxiety.